The 866, centered on the front, is the smaller Newer Lamb (with 921/922 on the loops on ends)..... This one is the larger 'Middle Lamb', which also has variations that have vent holes.... as best as we have figured... the progression of variations is ... No Vent Holes - Earlier Time Frame.... appearance and tweaking of the vent holes... moving forward thru Time...
Still on the hunt for the Leg Forward... someday.. someday.... ::)